A long straight current-carrying wire passes normally through the centre of a circular loop. If the current through the wire increases, will there be an induced emf in the loop? Justify.
Answer: No. The flux of the wire's field through the loop is always zero, so no emf is induced however the current changes.
Solution
The magnetic field of the long straight wire forms circles in the plane of the loop (the wire is perpendicular to the loop and passes through its centre).
These field lines lie in the plane of the loop, so they are parallel to the loop's area and pierce no part of it; the flux linked with the loop is zero at every instant.
Since always, even as the current (and hence the field) increases, so no emf is induced.
These field lines lie in the plane of the loop, so they are parallel to the loop's area and pierce no part of it; the flux linked with the loop is zero at every instant.
Since always, even as the current (and hence the field) increases, so no emf is induced.
CBSE Class 12 Board · 2017 · Delhi · Subjective